Core Internals

Some key internal constructs are listed here.

Object Name Description

AdaptedConnection

Interface of an adapted connection object to support the DBAPI protocol.

Compiled

Represent a compiled SQL or DDL expression.

DDLCompiler

DefaultDialect

Default implementation of Dialect

DefaultExecutionContext

Dialect

Define the behavior of a specific database and DB-API combination.

ExecutionContext

A messenger object for a Dialect that corresponds to a single execution.

GenericTypeCompiler

Identified

IdentifierPreparer

Handle quoting and case-folding of identifiers based on options.

SQLCompiler

Default implementation of Compiled.

StrSQLCompiler

A SQLCompiler subclass which allows a small selection of non-standard SQL features to render into a string value.
class sqlalchemy.engine.Compiled(dialect, statement, schema_translate_map=None, render_schema_translate=False, compile_kwargs={})

Represent a compiled SQL or DDL expression.

Members

__init__(), compile_state, construct_params(), dml_compile_state, execution_options, params, sql_compiler

The __str__ method of the Compiled object should produce the actual text of the statement. Compiled objects are specific to their underlying database dialect, and also may or may not be specific to the columns referenced within a particular set of bind parameters. In no case should the Compiled object be dependent on the actual values of those bind parameters, even though it may reference those values as defaults.

method sqlalchemy.engine.Compiled.__init__(dialect, statement, schema_translate_map=None, render_schema_translate=False, compile_kwargs={})

Construct a new Compiled object.

Parameters:

  • dialect – Dialect to compile against.

  • statement – ClauseElement to be compiled.

  • schema_translate_map –

    dictionary of schema names to be translated when forming the resultant SQL

    New in version 1.1.

    See also

    Translation of Schema Names

  • compile_kwargs – additional kwargs that will be passed to the initial call to Compiled.process().

attribute sqlalchemy.engine.Compiled.compile_state = None

Optional CompileState object that maintains additional state used by the compiler.

Major executable objects such as Insert, Update, Delete, Select will generate this state when compiled in order to calculate additional information about the object. For the top level object that is to be executed, the state can be stored here where it can also have applicability towards result set processing.

New in version 1.4.

method sqlalchemy.engine.Compiled.construct_params(params=None, extracted_parameters=None, escape_names=True)

Return the bind params for this compiled object.

Parameters:

params – a dict of string/object pairs whose values will override bind values compiled in to the statement.

attribute sqlalchemy.engine.Compiled.dml_compile_state = None

Optional CompileState assigned at the same point that .isinsert, .isupdate, or .isdelete is assigned.

This will normally be the same object as .compile_state, with the exception of cases like the ORMFromStatementCompileState object.

New in version 1.4.40.

attribute sqlalchemy.engine.Compiled.execution_options = {}

Execution options propagated from the statement. In some cases, sub-elements of the statement can modify these.

attribute sqlalchemy.engine.Compiled.params

Return the bind params for this compiled object.

attribute sqlalchemy.engine.Compiled.sql_compiler

Return a Compiled that is capable of processing SQL expressions.

If this compiler is one, it would likely just return ‘self’.

class sqlalchemy.sql.compiler.DDLCompiler(dialect, statement, schema_translate_map=None, render_schema_translate=False, compile_kwargs={})

Members

__init__(), compile_state, construct_params(), define_constraint_remote_table(), dml_compile_state, execution_options, params, sql_compiler

Class signature

class sqlalchemy.sql.compiler.DDLCompiler (sqlalchemy.sql.compiler.Compiled)

method sqlalchemy.sql.compiler.DDLCompiler.__init__(dialect, statement, schema_translate_map=None, render_schema_translate=False, compile_kwargs={})

inherited from the sqlalchemy.sql.compiler.Compiled.__init__ method of Compiled

Construct a new Compiled object.

Parameters:

  • dialect – Dialect to compile against.

  • statement – ClauseElement to be compiled.

  • schema_translate_map –

    dictionary of schema names to be translated when forming the resultant SQL

    New in version 1.1.

    See also

    Translation of Schema Names

  • compile_kwargs – additional kwargs that will be passed to the initial call to Compiled.process().

attribute sqlalchemy.sql.compiler.DDLCompiler.compile_state = None

inherited from the Compiled.compile_state attribute of Compiled

Optional CompileState object that maintains additional state used by the compiler.

Major executable objects such as Insert, Update, Delete, Select will generate this state when compiled in order to calculate additional information about the object. For the top level object that is to be executed, the state can be stored here where it can also have applicability towards result set processing.

New in version 1.4.

method sqlalchemy.sql.compiler.DDLCompiler.construct_params(params=None, extracted_parameters=None, escape_names=True)

Return the bind params for this compiled object.

Parameters:

params – a dict of string/object pairs whose values will override bind values compiled in to the statement.

method sqlalchemy.sql.compiler.DDLCompiler.define_constraint_remote_table(constraint, table, preparer)

Format the remote table clause of a CREATE CONSTRAINT clause.

attribute sqlalchemy.sql.compiler.DDLCompiler.dml_compile_state = None

inherited from the Compiled.dml_compile_state attribute of Compiled

Optional CompileState assigned at the same point that .isinsert, .isupdate, or .isdelete is assigned.

This will normally be the same object as .compile_state, with the exception of cases like the ORMFromStatementCompileState object.

New in version 1.4.40.

attribute sqlalchemy.sql.compiler.DDLCompiler.execution_options = {}

inherited from the Compiled.execution_options attribute of Compiled

Execution options propagated from the statement. In some cases, sub-elements of the statement can modify these.

attribute sqlalchemy.sql.compiler.DDLCompiler.params

inherited from the Compiled.params attribute of Compiled

Return the bind params for this compiled object.

attribute sqlalchemy.sql.compiler.DDLCompiler.sql_compiler
class sqlalchemy.engine.default.DefaultDialect(convert_unicode=False, encoding='utf-8', paramstyle=None, dbapi=None, implicit_returning=None, case_sensitive=True, supports_native_boolean=None, max_identifier_length=None, label_length=None, compiler_linting=0, server_side_cursors=False, **kwargs)

Default implementation of Dialect

Members

connect(), construct_arguments, create_connect_args(), create_xid(), dbapi_exception_translation_map, ddl_compiler, denormalize_name(), do_begin(), do_begin_twophase(), do_close(), do_commit(), do_commit_twophase(), do_execute(), do_execute_no_params(), do_executemany(), do_prepare_twophase(), do_recover_twophase(), do_release_savepoint(), do_rollback(), do_rollback_to_savepoint(), do_rollback_twophase(), do_savepoint(), do_set_input_sizes(), do_terminate(), engine_created(), execute_sequence_format, execution_ctx_cls, get_check_constraints(), get_columns(), get_default_isolation_level(), get_dialect_cls(), get_driver_connection(), get_foreign_keys(), get_indexes(), get_isolation_level(), get_pk_constraint(), get_sequence_names(), get_table_comment(), get_table_names(), get_temp_table_names(), get_temp_view_names(), get_unique_constraints(), get_view_definition(), get_view_names(), has_index(), has_sequence(), has_table(), initialize(), is_disconnect(), load_provisioning(), normalize_name(), on_connect(), on_connect_url(), preparer, reset_isolation_level(), returns_unicode_strings, set_isolation_level(), statement_compiler, supports_default_metavalue, supports_default_values, supports_empty_insert, supports_sane_rowcount_returning, supports_statement_cache, type_compiler, type_descriptor()

Class signature

class sqlalchemy.engine.default.DefaultDialect (sqlalchemy.engine.interfaces.Dialect)

method sqlalchemy.engine.default.DefaultDialect.connect(*cargs, **cparams)

Establish a connection using this dialect’s DBAPI.

The default implementation of this method is:

def connect(self, *cargs, **cparams):
    return self.dbapi.connect(*cargs, **cparams)

The *cargs, **cparams parameters are generated directly from this dialect’s Dialect.create_connect_args() method.

This method may be used for dialects that need to perform programmatic per-connection steps when a new connection is procured from the DBAPI.

Parameters:
Returns:

a DBAPI connection, typically from the PEP 249 module level .connect() function.

See also

Dialect.create_connect_args()

Dialect.on_connect()

attribute sqlalchemy.engine.default.DefaultDialect.construct_arguments = None

Optional set of argument specifiers for various SQLAlchemy constructs, typically schema items.

To implement, establish as a series of tuples, as in:

construct_arguments = [
    (schema.Index, {
        "using": False,
        "where": None,
        "ops": None
    })
]

If the above construct is established on the PostgreSQL dialect, the Index construct will now accept the keyword arguments postgresql_using, postgresql_where, nad postgresql_ops. Any other argument specified to the constructor of Index which is prefixed with postgresql_ will raise ArgumentError.

A dialect which does not include a construct_arguments member will not participate in the argument validation system. For such a dialect, any argument name is accepted by all participating constructs, within the namespace of arguments prefixed with that dialect name. The rationale here is so that third-party dialects that haven’t yet implemented this feature continue to function in the old way.

New in version 0.9.2.

See also

DialectKWArgs - implementing base class which consumes DefaultDialect.construct_arguments

method sqlalchemy.engine.default.DefaultDialect.create_connect_args(url)

Build DB-API compatible connection arguments.

Given a URL object, returns a tuple consisting of a (*args, **kwargs) suitable to send directly to the dbapi’s connect function. The arguments are sent to the Dialect.connect() method which then runs the DBAPI-level connect() function.

The method typically makes use of the URL.translate_connect_args() method in order to generate a dictionary of options.

The default implementation is:

def create_connect_args(self, url):
    opts = url.translate_connect_args()
    opts.update(url.query)
    return [[], opts]
Parameters:

url – a URL object

Returns:

a tuple of (*args, **kwargs) which will be passed to the Dialect.connect() method.

See also

URL.translate_connect_args()

method sqlalchemy.engine.default.DefaultDialect.create_xid()

Create a random two-phase transaction ID.

This id will be passed to do_begin_twophase(), do_rollback_twophase(), do_commit_twophase(). Its format is unspecified.

attribute sqlalchemy.engine.default.DefaultDialect.dbapi_exception_translation_map = {}

mapping used in the extremely unusual case that a DBAPI’s published exceptions don’t actually have the __name__ that they are linked towards.

New in version 1.0.5.

attribute sqlalchemy.engine.default.DefaultDialect.ddl_compiler

alias of DDLCompiler

method sqlalchemy.engine.default.DefaultDialect.denormalize_name(name)

convert the given name to a case insensitive identifier for the backend if it is an all-lowercase name.

This method is only used if the dialect defines requires_name_normalize=True.

method sqlalchemy.engine.default.DefaultDialect.do_begin(dbapi_connection)

Provide an implementation of connection.begin(), given a DB-API connection.

The DBAPI has no dedicated “begin” method and it is expected that transactions are implicit. This hook is provided for those DBAPIs that might need additional help in this area.

Note that Dialect.do_begin() is not called unless a Transaction object is in use. The Dialect.do_autocommit() hook is provided for DBAPIs that need some extra commands emitted after a commit in order to enter the next transaction, when the SQLAlchemy Connection is used in its default “autocommit” mode.

Parameters:

dbapi_connection – a DBAPI connection, typically proxied within a ConnectionFairy.

method sqlalchemy.engine.default.DefaultDialect.do_begin_twophase(connection, xid)

inherited from the Dialect.do_begin_twophase() method of Dialect

Begin a two phase transaction on the given connection.

Parameters:
method sqlalchemy.engine.default.DefaultDialect.do_close(dbapi_connection)

Provide an implementation of connection.close(), given a DBAPI connection.

This hook is called by the Pool when a connection has been detached from the pool, or is being returned beyond the normal capacity of the pool.

method sqlalchemy.engine.default.DefaultDialect.do_commit(dbapi_connection)

Provide an implementation of connection.commit(), given a DB-API connection.

Parameters:

dbapi_connection – a DBAPI connection, typically proxied within a ConnectionFairy.

method sqlalchemy.engine.default.DefaultDialect.do_commit_twophase(connection, xid, is_prepared=True, recover=False)

inherited from the Dialect.do_commit_twophase() method of Dialect

Commit a two phase transaction on the given connection.

Parameters:
method sqlalchemy.engine.default.DefaultDialect.do_execute(cursor, statement, parameters, context=None)

Provide an implementation of cursor.execute(statement, parameters).

method sqlalchemy.engine.default.DefaultDialect.do_execute_no_params(cursor, statement, context=None)

Provide an implementation of cursor.execute(statement).

The parameter collection should not be sent.

method sqlalchemy.engine.default.DefaultDialect.do_executemany(cursor, statement, parameters, context=None)

Provide an implementation of cursor.executemany(statement, parameters).

method sqlalchemy.engine.default.DefaultDialect.do_prepare_twophase(connection, xid)

inherited from the Dialect.do_prepare_twophase() method of Dialect

Prepare a two phase transaction on the given connection.

Parameters:
method sqlalchemy.engine.default.DefaultDialect.do_recover_twophase(connection)

inherited from the Dialect.do_recover_twophase() method of Dialect

Recover list of uncommitted prepared two phase transaction identifiers on the given connection.

Parameters:

connection – a Connection.

method sqlalchemy.engine.default.DefaultDialect.do_release_savepoint(connection, name)

Release the named savepoint on a connection.

Parameters:
method sqlalchemy.engine.default.DefaultDialect.do_rollback(dbapi_connection)

Provide an implementation of connection.rollback(), given a DB-API connection.

Parameters:

dbapi_connection – a DBAPI connection, typically proxied within a ConnectionFairy.

method sqlalchemy.engine.default.DefaultDialect.do_rollback_to_savepoint(connection, name)

Rollback a connection to the named savepoint.

Parameters:
method sqlalchemy.engine.default.DefaultDialect.do_rollback_twophase(connection, xid, is_prepared=True, recover=False)

inherited from the Dialect.do_rollback_twophase() method of Dialect

Rollback a two phase transaction on the given connection.

Parameters:
method sqlalchemy.engine.default.DefaultDialect.do_savepoint(connection, name)

Create a savepoint with the given name.

Parameters:
method sqlalchemy.engine.default.DefaultDialect.do_set_input_sizes(cursor, list_of_tuples, context)

inherited from the Dialect.do_set_input_sizes() method of Dialect

invoke the cursor.setinputsizes() method with appropriate arguments

This hook is called if the dialect.use_inputsizes flag is set to True. Parameter data is passed in a list of tuples (paramname, dbtype, sqltype), where paramname is the key of the parameter in the statement, dbtype is the DBAPI datatype and sqltype is the SQLAlchemy type. The order of tuples is in the correct parameter order.

New in version 1.4.

method sqlalchemy.engine.default.DefaultDialect.do_terminate(dbapi_connection)

Provide an implementation of connection.close() that tries as much as possible to not block, given a DBAPI connection.

In the vast majority of cases this just calls .close(), however for some asyncio dialects may call upon different API features.

This hook is called by the Pool when a connection is being recycled or has been invalidated.

New in version 1.4.41.

classmethod sqlalchemy.engine.default.DefaultDialect.engine_created(engine)

inherited from the Dialect.engine_created() method of Dialect

A convenience hook called before returning the final Engine.

If the dialect returned a different class from the get_dialect_cls() method, then the hook is called on both classes, first on the dialect class returned by the get_dialect_cls() method and then on the class on which the method was called.

The hook should be used by dialects and/or wrappers to apply special events to the engine or its components. In particular, it allows a dialect-wrapping class to apply dialect-level events.

New in version 1.0.3.

attribute sqlalchemy.engine.default.DefaultDialect.execute_sequence_format

alias of tuple

attribute sqlalchemy.engine.default.DefaultDialect.execution_ctx_cls

alias of DefaultExecutionContext

method sqlalchemy.engine.default.DefaultDialect.get_check_constraints(connection, table_name, schema=None, **kw)

inherited from the Dialect.get_check_constraints() method of Dialect

Return information about check constraints in table_name.

Given a string table_name and an optional string schema, return check constraint information as a list of dicts with these keys:

  • name - the check constraint’s name

  • sqltext - the check constraint’s SQL expression

  • **kw - other options passed to the dialect’s get_check_constraints() method.

New in version 1.1.0.

method sqlalchemy.engine.default.DefaultDialect.get_columns(connection, table_name, schema=None, **kw)

inherited from the Dialect.get_columns() method of Dialect

Return information about columns in table_name.

Given a Connection, a string table_name, and an optional string schema, return column information as a list of dictionaries with these keys:

name

the column’s name

type

[sqlalchemy.types#TypeEngine]

nullable

boolean

default

the column’s default value

autoincrement

boolean

sequence
a dictionary of the form
{‘name’str, ‘start’ :int, ‘increment’: int, ‘minvalue’: int,

‘maxvalue’: int, ‘nominvalue’: bool, ‘nomaxvalue’: bool, ‘cycle’: bool, ‘cache’: int, ‘order’: bool}

Additional column attributes may be present.

method sqlalchemy.engine.default.DefaultDialect.get_default_isolation_level(dbapi_conn)

Given a DBAPI connection, return its isolation level, or a default isolation level if one cannot be retrieved.

May be overridden by subclasses in order to provide a “fallback” isolation level for databases that cannot reliably retrieve the actual isolation level.

By default, calls the Interfaces.get_isolation_level() method, propagating any exceptions raised.

New in version 1.3.22.

classmethod sqlalchemy.engine.default.DefaultDialect.get_dialect_cls(url)

inherited from the Dialect.get_dialect_cls() method of Dialect

Given a URL, return the Dialect that will be used.

This is a hook that allows an external plugin to provide functionality around an existing dialect, by allowing the plugin to be loaded from the url based on an entrypoint, and then the plugin returns the actual dialect to be used.

By default this just returns the cls.

New in version 1.0.3.

method sqlalchemy.engine.default.DefaultDialect.get_driver_connection(connection)

Returns the connection object as returned by the external driver package.

For normal dialects that use a DBAPI compliant driver this call will just return the connection passed as argument. For dialects that instead adapt a non DBAPI compliant driver, like when adapting an asyncio driver, this call will return the connection-like object as returned by the driver.

New in version 1.4.24.

method sqlalchemy.engine.default.DefaultDialect.get_foreign_keys(connection, table_name, schema=None, **kw)

inherited from the Dialect.get_foreign_keys() method of Dialect

Return information about foreign_keys in table_name.

Given a Connection, a string table_name, and an optional string schema, return foreign key information as a list of dicts with these keys:

name

the constraint’s name

constrained_columns

a list of column names that make up the foreign key

referred_schema

the name of the referred schema

referred_table

the name of the referred table

referred_columns

a list of column names in the referred table that correspond to constrained_columns

method sqlalchemy.engine.default.DefaultDialect.get_indexes(connection, table_name, schema=None, **kw)

inherited from the Dialect.get_indexes() method of Dialect

Return information about indexes in table_name.

Given a Connection, a string table_name and an optional string schema, return index information as a list of dictionaries with these keys:

name

the index’s name

column_names

list of column names in order

unique

boolean

method sqlalchemy.engine.default.DefaultDialect.get_isolation_level(dbapi_conn)

inherited from the Dialect.get_isolation_level() method of Dialect

Given a DBAPI connection, return its isolation level.

When working with a Connection object, the corresponding DBAPI connection may be procured using the Connection.connection accessor.

Note that this is a dialect-level method which is used as part of the implementation of the Connection and Engine isolation level facilities; these APIs should be preferred for most typical use cases.

See also

Connection.get_isolation_level() - view current level

Connection.default_isolation_level - view default level

Connection.execution_options.isolation_level - set per Connection isolation level

create_engine.isolation_level - set per Engine isolation level

method sqlalchemy.engine.default.DefaultDialect.get_pk_constraint(connection, table_name, schema=None, **kw)

inherited from the Dialect.get_pk_constraint() method of Dialect

Return information about the primary key constraint on table_name`.

Given a Connection, a string table_name, and an optional string schema, return primary key information as a dictionary with these keys:

constrained_columns

a list of column names that make up the primary key

name

optional name of the primary key constraint.

method sqlalchemy.engine.default.DefaultDialect.get_sequence_names(connection, schema=None, **kw)

inherited from the Dialect.get_sequence_names() method of Dialect

Return a list of all sequence names available in the database.

Parameters:

schema – schema name to query, if not the default schema.

New in version 1.4.

method sqlalchemy.engine.default.DefaultDialect.get_table_comment(connection, table_name, schema=None, **kw)

inherited from the Dialect.get_table_comment() method of Dialect

Return the “comment” for the table identified by table_name.

Given a string table_name and an optional string schema, return table comment information as a dictionary with this key:

text

text of the comment

Raises NotImplementedError for dialects that don’t support comments.

New in version 1.2.

method sqlalchemy.engine.default.DefaultDialect.get_table_names(connection, schema=None, **kw)

inherited from the Dialect.get_table_names() method of Dialect

Return a list of table names for schema.

method sqlalchemy.engine.default.DefaultDialect.get_temp_table_names(connection, schema=None, **kw)

inherited from the Dialect.get_temp_table_names() method of Dialect

Return a list of temporary table names on the given connection, if supported by the underlying backend.

method sqlalchemy.engine.default.DefaultDialect.get_temp_view_names(connection, schema=None, **kw)

inherited from the Dialect.get_temp_view_names() method of Dialect

Return a list of temporary view names on the given connection, if supported by the underlying backend.

method sqlalchemy.engine.default.DefaultDialect.get_unique_constraints(connection, table_name, schema=None, **kw)

inherited from the Dialect.get_unique_constraints() method of Dialect

Return information about unique constraints in table_name.

Given a string table_name and an optional string schema, return unique constraint information as a list of dicts with these keys:

name

the unique constraint’s name

column_names

list of column names in order

**kw

other options passed to the dialect’s get_unique_constraints() method.

New in version 0.9.0.

method sqlalchemy.engine.default.DefaultDialect.get_view_definition(connection, view_name, schema=None, **kw)

inherited from the Dialect.get_view_definition() method of Dialect

Return view definition.

Given a Connection, a string view_name, and an optional string schema, return the view definition.

method sqlalchemy.engine.default.DefaultDialect.get_view_names(connection, schema=None, **kw)

inherited from the Dialect.get_view_names() method of Dialect

Return a list of all view names available in the database.

Parameters:

schema – schema name to query, if not the default schema.

method sqlalchemy.engine.default.DefaultDialect.has_index(connection, table_name, index_name, schema=None)

Check the existence of a particular index name in the database.

Given a Connection object, a string table_name and string index name, return True if an index of the given name on the given table exists, false otherwise.

The DefaultDialect implements this in terms of the Dialect.has_table() and Dialect.get_indexes() methods, however dialects can implement a more performant version.

New in version 1.4.

method sqlalchemy.engine.default.DefaultDialect.has_sequence(connection, sequence_name, schema=None, **kw)

inherited from the Dialect.has_sequence() method of Dialect

Check the existence of a particular sequence in the database.

Given a Connection object and a string sequence_name, return True if the given sequence exists in the database, False otherwise.

method sqlalchemy.engine.default.DefaultDialect.has_table(connection, table_name, schema=None, **kw)

inherited from the Dialect.has_table() method of Dialect

For internal dialect use, check the existence of a particular table in the database.

Given a Connection object, a string table_name and optional schema name, return True if the given table exists in the database, False otherwise.

This method serves as the underlying implementation of the public facing Inspector.has_table() method, and is also used internally to implement the “checkfirst” behavior for methods like Table.create() and MetaData.create_all().

Note

This method is used internally by SQLAlchemy, and is published so that third-party dialects may provide an implementation. It is not the public API for checking for table presence. Please use the Inspector.has_table() method. Alternatively, for legacy cross-compatibility, the Engine.has_table() method may be used.

method sqlalchemy.engine.default.DefaultDialect.initialize(connection)

Called during strategized creation of the dialect with a connection.

Allows dialects to configure options based on server version info or other properties.

The connection passed here is a SQLAlchemy Connection object, with full capabilities.

The initialize() method of the base dialect should be called via super().

Note

as of SQLAlchemy 1.4, this method is called before any Dialect.on_connect() hooks are called.

method sqlalchemy.engine.default.DefaultDialect.is_disconnect(e, connection, cursor)

Return True if the given DB-API error indicates an invalid connection

classmethod sqlalchemy.engine.default.DefaultDialect.load_provisioning()

set up the provision.py module for this dialect.

For dialects that include a provision.py module that sets up provisioning followers, this method should initiate that process.

A typical implementation would be:

@classmethod
def load_provisioning(cls):
    __import__("mydialect.provision")

The default method assumes a module named provision.py inside the owning package of the current dialect, based on the __module__ attribute:

@classmethod
def load_provisioning(cls):
    package = ".".join(cls.__module__.split(".")[0:-1])
    try:
        __import__(package + ".provision")
    except ImportError:
        pass

New in version 1.3.14.

method sqlalchemy.engine.default.DefaultDialect.normalize_name(name)

convert the given name to lowercase if it is detected as case insensitive.

This method is only used if the dialect defines requires_name_normalize=True.

method sqlalchemy.engine.default.DefaultDialect.on_connect()

return a callable which sets up a newly created DBAPI connection.

The callable should accept a single argument “conn” which is the DBAPI connection itself. The inner callable has no return value.

E.g.:

class MyDialect(default.DefaultDialect):
    # ...

    def on_connect(self):
        def do_on_connect(connection):
            connection.execute("SET SPECIAL FLAGS etc")

        return do_on_connect

This is used to set dialect-wide per-connection options such as isolation modes, Unicode modes, etc.

The “do_on_connect” callable is invoked by using the PoolEvents.connect() event hook, then unwrapping the DBAPI connection and passing it into the callable.

Changed in version 1.4: the on_connect hook is no longer called twice for the first connection of a dialect. The on_connect hook is still called before the Dialect.initialize() method however.

Changed in version 1.4.3: the on_connect hook is invoked from a new method on_connect_url that passes the URL that was used to create the connect args. Dialects can implement on_connect_url instead of on_connect if they need the URL object that was used for the connection in order to get additional context.

If None is returned, no event listener is generated.

Returns:

a callable that accepts a single DBAPI connection as an argument, or None.

See also

Dialect.connect() - allows the DBAPI connect() sequence itself to be controlled.

Dialect.on_connect_url() - supersedes Dialect.on_connect() to also receive the URL object in context.

method sqlalchemy.engine.default.DefaultDialect.on_connect_url(url)

inherited from the Dialect.on_connect_url() method of Dialect

return a callable which sets up a newly created DBAPI connection.

This method is a new hook that supersedes the Dialect.on_connect() method when implemented by a dialect. When not implemented by a dialect, it invokes the Dialect.on_connect() method directly to maintain compatibility with existing dialects. There is no deprecation for Dialect.on_connect() expected.

The callable should accept a single argument “conn” which is the DBAPI connection itself. The inner callable has no return value.

E.g.:

class MyDialect(default.DefaultDialect):
    # ...

    def on_connect_url(self, url):
        def do_on_connect(connection):
            connection.execute("SET SPECIAL FLAGS etc")

        return do_on_connect

This is used to set dialect-wide per-connection options such as isolation modes, Unicode modes, etc.

This method differs from Dialect.on_connect() in that it is passed the URL object that’s relevant to the connect args. Normally the only way to get this is from the Dialect.on_connect() hook is to look on the Engine itself, however this URL object may have been replaced by plugins.

Note

The default implementation of Dialect.on_connect_url() is to invoke the Dialect.on_connect() method. Therefore if a dialect implements this method, the Dialect.on_connect() method will not be called unless the overriding dialect calls it directly from here.

New in version 1.4.3: added Dialect.on_connect_url() which normally calls into Dialect.on_connect().

Parameters:

url – a URL object representing the URL that was passed to the Dialect.create_connect_args() method.

Returns:

a callable that accepts a single DBAPI connection as an argument, or None.

See also

Dialect.on_connect()

attribute sqlalchemy.engine.default.DefaultDialect.preparer

alias of IdentifierPreparer

method sqlalchemy.engine.default.DefaultDialect.reset_isolation_level(dbapi_conn)

Given a DBAPI connection, revert its isolation to the default.

Note that this is a dialect-level method which is used as part of the implementation of the Connection and Engine isolation level facilities; these APIs should be preferred for most typical use cases.

See also

Connection.get_isolation_level() - view current level

Connection.default_isolation_level - view default level

Connection.execution_options.isolation_level - set per Connection isolation level

create_engine.isolation_level - set per Engine isolation level

attribute sqlalchemy.engine.default.DefaultDialect.returns_unicode_strings = symbol('RETURNS_UNICODE')
method sqlalchemy.engine.default.DefaultDialect.set_isolation_level(dbapi_conn, level)

inherited from the Dialect.set_isolation_level() method of Dialect

Given a DBAPI connection, set its isolation level.

Note that this is a dialect-level method which is used as part of the implementation of the Connection and Engine isolation level facilities; these APIs should be preferred for most typical use cases.

See also

Connection.get_isolation_level() - view current level

Connection.default_isolation_level - view default level

Connection.execution_options.isolation_level - set per Connection isolation level

create_engine.isolation_level - set per Engine isolation level

attribute sqlalchemy.engine.default.DefaultDialect.statement_compiler

alias of SQLCompiler

attribute sqlalchemy.engine.default.DefaultDialect.supports_default_metavalue = False

dialect supports INSERT… VALUES (DEFAULT) syntax

attribute sqlalchemy.engine.default.DefaultDialect.supports_default_values = False

dialect supports INSERT… DEFAULT VALUES syntax

attribute sqlalchemy.engine.default.DefaultDialect.supports_empty_insert = True

dialect supports INSERT () VALUES ()

attribute sqlalchemy.engine.default.DefaultDialect.supports_sane_rowcount_returning

True if this dialect supports sane rowcount even if RETURNING is in use.

For dialects that don’t support RETURNING, this is synonymous with supports_sane_rowcount.

attribute sqlalchemy.engine.default.DefaultDialect.supports_statement_cache = True

indicates if this dialect supports caching.

All dialects that are compatible with statement caching should set this flag to True directly on each dialect class and subclass that supports it. SQLAlchemy tests that this flag is locally present on each dialect subclass before it will use statement caching. This is to provide safety for legacy or new dialects that are not yet fully tested to be compliant with SQL statement caching.

New in version 1.4.5.

See also

Caching for Third Party Dialects

attribute sqlalchemy.engine.default.DefaultDialect.type_compiler

alias of GenericTypeCompiler

method sqlalchemy.engine.default.DefaultDialect.type_descriptor(typeobj)

Provide a database-specific TypeEngine object, given the generic object which comes from the types module.

This method looks for a dictionary called colspecs as a class or instance-level variable, and passes on to adapt_type().

class sqlalchemy.engine.Dialect

Define the behavior of a specific database and DB-API combination.

Any aspect of metadata definition, SQL query generation, execution, result-set handling, or anything else which varies between databases is defined under the general category of the Dialect. The Dialect acts as a factory for other database-specific object implementations including ExecutionContext, Compiled, DefaultGenerator, and TypeEngine.

Note

Third party dialects should not subclass Dialect directly. Instead, subclass DefaultDialect or descendant class.

All dialects include the following attributes. There are many other attributes that may be supported as well:

Members

connect(), create_connect_args(), create_xid(), denormalize_name(), do_begin(), do_begin_twophase(), do_close(), do_commit(), do_commit_twophase(), do_execute(), do_execute_no_params(), do_executemany(), do_prepare_twophase(), do_recover_twophase(), do_release_savepoint(), do_rollback(), do_rollback_to_savepoint(), do_rollback_twophase(), do_savepoint(), do_set_input_sizes(), do_terminate(), engine_created(), get_check_constraints(), get_columns(), get_default_isolation_level(), get_dialect_cls(), get_driver_connection(), get_foreign_keys(), get_indexes(), get_isolation_level(), get_pk_constraint(), get_sequence_names(), get_table_comment(), get_table_names(), get_temp_table_names(), get_temp_view_names(), get_unique_constraints(), get_view_definition(), get_view_names(), has_index(), has_sequence(), has_table(), initialize(), is_disconnect(), load_provisioning(), normalize_name(), on_connect(), on_connect_url(), reset_isolation_level(), set_isolation_level(), supports_statement_cache, type_descriptor()

name

identifying name for the dialect from a DBAPI-neutral point of view (i.e. ‘sqlite’)

driver

identifying name for the dialect’s DBAPI

positional

True if the paramstyle for this Dialect is positional.

paramstyle

the paramstyle to be used (some DB-APIs support multiple paramstyles).

encoding

type of encoding to use for unicode, usually defaults to ‘utf-8’.

statement_compiler

a Compiled class used to compile SQL statements

ddl_compiler

a Compiled class used to compile DDL statements

server_version_info

a tuple containing a version number for the DB backend in use. This value is only available for supporting dialects, and is typically populated during the initial connection to the database.

default_schema_name

the name of the default schema. This value is only available for supporting dialects, and is typically populated during the initial connection to the database.

execution_ctx_cls

a ExecutionContext class used to handle statement execution

execute_sequence_format

either the ‘tuple’ or ‘list’ type, depending on what cursor.execute() accepts for the second argument (they vary).

preparer

a IdentifierPreparer class used to quote identifiers.

supports_alter

True if the database supports ALTER TABLE - used only for generating foreign key constraints in certain circumstances

max_identifier_length

The maximum length of identifier names.

supports_sane_rowcount

Indicate whether the dialect properly implements rowcount for UPDATE and DELETE statements.

supports_sane_multi_rowcount

Indicate whether the dialect properly implements rowcount for UPDATE and DELETE statements when executed via executemany.

preexecute_autoincrement_sequences

True if ‘implicit’ primary key functions must be executed separately in order to get their value. This is currently oriented towards PostgreSQL.

implicit_returning

use RETURNING or equivalent during INSERT execution in order to load newly generated primary keys and other column defaults in one execution, which are then available via inserted_primary_key. If an insert statement has returning() specified explicitly, the “implicit” functionality is not used and inserted_primary_key will not be available.

colspecs

A dictionary of TypeEngine classes from sqlalchemy.types mapped to subclasses that are specific to the dialect class. This dictionary is class-level only and is not accessed from the dialect instance itself.

supports_default_values

Indicates if the construct INSERT INTO tablename DEFAULT VALUES is supported

supports_sequences

Indicates if the dialect supports CREATE SEQUENCE or similar.

sequences_optional

If True, indicates if the “optional” flag on the Sequence() construct should signal to not generate a CREATE SEQUENCE. Applies only to dialects that support sequences. Currently used only to allow PostgreSQL SERIAL to be used on a column that specifies Sequence() for usage on other backends.

supports_native_enum

Indicates if the dialect supports a native ENUM construct. This will prevent types.Enum from generating a CHECK constraint when that type is used.

supports_native_boolean

Indicates if the dialect supports a native boolean construct. This will prevent types.Boolean from generating a CHECK constraint when that type is used.

dbapi_exception_translation_map

A dictionary of names that will contain as values the names of pep-249 exceptions (“IntegrityError”, “OperationalError”, etc) keyed to alternate class names, to support the case where a DBAPI has exception classes that aren’t named as they are referred to (e.g. IntegrityError = MyException). In the vast majority of cases this dictionary is empty.

New in version 1.0.5.

method sqlalchemy.engine.Dialect.connect(*cargs, **cparams)

Establish a connection using this dialect’s DBAPI.

The default implementation of this method is:

def connect(self, *cargs, **cparams):
    return self.dbapi.connect(*cargs, **cparams)

The *cargs, **cparams parameters are generated directly from this dialect’s Dialect.create_connect_args() method.

This method may be used for dialects that need to perform programmatic per-connection steps when a new connection is procured from the DBAPI.

Parameters:
Returns:

a DBAPI connection, typically from the PEP 249 module level .connect() function.

See also

Dialect.create_connect_args()

Dialect.on_connect()

method sqlalchemy.engine.Dialect.create_connect_args(url)

Build DB-API compatible connection arguments.

Given a URL object, returns a tuple consisting of a (*args, **kwargs) suitable to send directly to the dbapi’s connect function. The arguments are sent to the Dialect.connect() method which then runs the DBAPI-level connect() function.

The method typically makes use of the URL.translate_connect_args() method in order to generate a dictionary of options.

The default implementation is:

def create_connect_args(self, url):
    opts = url.translate_connect_args()
    opts.update(url.query)
    return [[], opts]
Parameters:

url – a URL object

Returns:

a tuple of (*args, **kwargs) which will be passed to the Dialect.connect() method.

See also

URL.translate_connect_args()

method sqlalchemy.engine.Dialect.create_xid()

Create a two-phase transaction ID.

This id will be passed to do_begin_twophase(), do_rollback_twophase(), do_commit_twophase(). Its format is unspecified.

method sqlalchemy.engine.Dialect.denormalize_name(name)

convert the given name to a case insensitive identifier for the backend if it is an all-lowercase name.

This method is only used if the dialect defines requires_name_normalize=True.

method sqlalchemy.engine.Dialect.do_begin(dbapi_connection)

Provide an implementation of connection.begin(), given a DB-API connection.

The DBAPI has no dedicated “begin” method and it is expected that transactions are implicit. This hook is provided for those DBAPIs that might need additional help in this area.

Note that Dialect.do_begin() is not called unless a Transaction object is in use. The Dialect.do_autocommit() hook is provided for DBAPIs that need some extra commands emitted after a commit in order to enter the next transaction, when the SQLAlchemy Connection is used in its default “autocommit” mode.

Parameters:

dbapi_connection – a DBAPI connection, typically proxied within a ConnectionFairy.

method sqlalchemy.engine.Dialect.do_begin_twophase(connection, xid)

Begin a two phase transaction on the given connection.

Parameters:
method sqlalchemy.engine.Dialect.do_close(dbapi_connection)

Provide an implementation of connection.close(), given a DBAPI connection.

This hook is called by the Pool when a connection has been detached from the pool, or is being returned beyond the normal capacity of the pool.

method sqlalchemy.engine.Dialect.do_commit(dbapi_connection)

Provide an implementation of connection.commit(), given a DB-API connection.

Parameters:

dbapi_connection – a DBAPI connection, typically proxied within a ConnectionFairy.

method sqlalchemy.engine.Dialect.do_commit_twophase(connection, xid, is_prepared=True, recover=False)

Commit a two phase transaction on the given connection.

Parameters:
method sqlalchemy.engine.Dialect.do_execute(cursor, statement, parameters, context=None)

Provide an implementation of cursor.execute(statement, parameters).

method sqlalchemy.engine.Dialect.do_execute_no_params(cursor, statement, parameters, context=None)

Provide an implementation of cursor.execute(statement).

The parameter collection should not be sent.

method sqlalchemy.engine.Dialect.do_executemany(cursor, statement, parameters, context=None)

Provide an implementation of cursor.executemany(statement, parameters).

method sqlalchemy.engine.Dialect.do_prepare_twophase(connection, xid)

Prepare a two phase transaction on the given connection.

Parameters:
method sqlalchemy.engine.Dialect.do_recover_twophase(connection)

Recover list of uncommitted prepared two phase transaction identifiers on the given connection.

Parameters:

connection – a Connection.

method sqlalchemy.engine.Dialect.do_release_savepoint(connection, name)

Release the named savepoint on a connection.

Parameters:
method sqlalchemy.engine.Dialect.do_rollback(dbapi_connection)

Provide an implementation of connection.rollback(), given a DB-API connection.

Parameters:

dbapi_connection – a DBAPI connection, typically proxied within a ConnectionFairy.

method sqlalchemy.engine.Dialect.do_rollback_to_savepoint(connection, name)

Rollback a connection to the named savepoint.

Parameters:
method sqlalchemy.engine.Dialect.do_rollback_twophase(connection, xid, is_prepared=True, recover=False)

Rollback a two phase transaction on the given connection.

Parameters:
method sqlalchemy.engine.Dialect.do_savepoint(connection, name)

Create a savepoint with the given name.

Parameters:
method sqlalchemy.engine.Dialect.do_set_input_sizes(cursor, list_of_tuples, context)

invoke the cursor.setinputsizes() method with appropriate arguments

This hook is called if the dialect.use_inputsizes flag is set to True. Parameter data is passed in a list of tuples (paramname, dbtype, sqltype), where paramname is the key of the parameter in the statement, dbtype is the DBAPI datatype and sqltype is the SQLAlchemy type. The order of tuples is in the correct parameter order.

New in version 1.4.

method sqlalchemy.engine.Dialect.do_terminate(dbapi_connection)

Provide an implementation of connection.close() that tries as much as possible to not block, given a DBAPI connection.

In the vast majority of cases this just calls .close(), however for some asyncio dialects may call upon different API features.

This hook is called by the Pool when a connection is being recycled or has been invalidated.

New in version 1.4.41.

classmethod sqlalchemy.engine.Dialect.engine_created(engine)

A convenience hook called before returning the final Engine.

If the dialect returned a different class from the get_dialect_cls() method, then the hook is called on both classes, first on the dialect class returned by the get_dialect_cls() method and then on the class on which the method was called.

The hook should be used by dialects and/or wrappers to apply special events to the engine or its components. In particular, it allows a dialect-wrapping class to apply dialect-level events.

New in version 1.0.3.

method sqlalchemy.engine.Dialect.get_check_constraints(connection, table_name, schema=None, **kw)

Return information about check constraints in table_name.

Given a string table_name and an optional string schema, return check constraint information as a list of dicts with these keys:

  • name - the check constraint’s name

  • sqltext - the check constraint’s SQL expression

  • **kw - other options passed to the dialect’s get_check_constraints() method.

New in version 1.1.0.

method sqlalchemy.engine.Dialect.get_columns(connection, table_name, schema=None, **kw)

Return information about columns in table_name.

Given a Connection, a string table_name, and an optional string schema, return column information as a list of dictionaries with these keys:

name

the column’s name

type

[sqlalchemy.types#TypeEngine]

nullable

boolean

default

the column’s default value

autoincrement

boolean

sequence
a dictionary of the form
{‘name’str, ‘start’ :int, ‘increment’: int, ‘minvalue’: int,

‘maxvalue’: int, ‘nominvalue’: bool, ‘nomaxvalue’: bool, ‘cycle’: bool, ‘cache’: int, ‘order’: bool}

Additional column attributes may be present.

method sqlalchemy.engine.Dialect.get_default_isolation_level(dbapi_conn)

Given a DBAPI connection, return its isolation level, or a default isolation level if one cannot be retrieved.

This method may only raise NotImplementedError and must not raise any other exception, as it is used implicitly upon first connect.

The method must return a value for a dialect that supports isolation level settings, as this level is what will be reverted towards when a per-connection isolation level change is made.

The method defaults to using the Dialect.get_isolation_level() method unless overridden by a dialect.

New in version 1.3.22.

classmethod sqlalchemy.engine.Dialect.get_dialect_cls(url)

Given a URL, return the Dialect that will be used.

This is a hook that allows an external plugin to provide functionality around an existing dialect, by allowing the plugin to be loaded from the url based on an entrypoint, and then the plugin returns the actual dialect to be used.

By default this just returns the cls.

New in version 1.0.3.

method sqlalchemy.engine.Dialect.get_driver_connection(connection)

Returns the connection object as returned by the external driver package.

For normal dialects that use a DBAPI compliant driver this call will just return the connection passed as argument. For dialects that instead adapt a non DBAPI compliant driver, like when adapting an asyncio driver, this call will return the connection-like object as returned by the driver.

New in version 1.4.24.

method sqlalchemy.engine.Dialect.get_foreign_keys(connection, table_name, schema=None, **kw)

Return information about foreign_keys in table_name.

Given a Connection, a string table_name, and an optional string schema, return foreign key information as a list of dicts with these keys:

name

the constraint’s name

constrained_columns

a list of column names that make up the foreign key

referred_schema

the name of the referred schema

referred_table

the name of the referred table

referred_columns

a list of column names in the referred table that correspond to constrained_columns

method sqlalchemy.engine.Dialect.get_indexes(connection, table_name, schema=None, **kw)

Return information about indexes in table_name.

Given a Connection, a string table_name and an optional string schema, return index information as a list of dictionaries with these keys:

name

the index’s name

column_names

list of column names in order

unique

boolean

method sqlalchemy.engine.Dialect.get_isolation_level(dbapi_conn)

Given a DBAPI connection, return its isolation level.

When working with a Connection object, the corresponding DBAPI connection may be procured using the Connection.connection accessor.

Note that this is a dialect-level method which is used as part of the implementation of the Connection and Engine isolation level facilities; these APIs should be preferred for most typical use cases.

See also

Connection.get_isolation_level() - view current level

Connection.default_isolation_level - view default level

Connection.execution_options.isolation_level - set per Connection isolation level

create_engine.isolation_level - set per Engine isolation level

method sqlalchemy.engine.Dialect.get_pk_constraint(connection, table_name, schema=None, **kw)

Return information about the primary key constraint on table_name`.

Given a Connection, a string table_name, and an optional string schema, return primary key information as a dictionary with these keys:

constrained_columns

a list of column names that make up the primary key

name

optional name of the primary key constraint.

method sqlalchemy.engine.Dialect.get_sequence_names(connection, schema=None, **kw)

Return a list of all sequence names available in the database.

Parameters:

schema – schema name to query, if not the default schema.

New in version 1.4.

method sqlalchemy.engine.Dialect.get_table_comment(connection, table_name, schema=None, **kw)

Return the “comment” for the table identified by table_name.

Given a string table_name and an optional string schema, return table comment information as a dictionary with this key:

text

text of the comment

Raises NotImplementedError for dialects that don’t support comments.

New in version 1.2.

method sqlalchemy.engine.Dialect.get_table_names(connection, schema=None, **kw)

Return a list of table names for schema.

method sqlalchemy.engine.Dialect.get_temp_table_names(connection, schema=None, **kw)

Return a list of temporary table names on the given connection, if supported by the underlying backend.

method sqlalchemy.engine.Dialect.get_temp_view_names(connection, schema=None, **kw)

Return a list of temporary view names on the given connection, if supported by the underlying backend.

method sqlalchemy.engine.Dialect.get_unique_constraints(connection, table_name, schema=None, **kw)

Return information about unique constraints in table_name.

Given a string table_name and an optional string schema, return unique constraint information as a list of dicts with these keys:

name

the unique constraint’s name

column_names

list of column names in order

**kw

other options passed to the dialect’s get_unique_constraints() method.

New in version 0.9.0.

method sqlalchemy.engine.Dialect.get_view_definition(connection, view_name, schema=None, **kw)

Return view definition.

Given a Connection, a string view_name, and an optional string schema, return the view definition.

method sqlalchemy.engine.Dialect.get_view_names(connection, schema=None, **kw)

Return a list of all view names available in the database.

Parameters:

schema – schema name to query, if not the default schema.

method sqlalchemy.engine.Dialect.has_index(connection, table_name, index_name, schema=None)

Check the existence of a particular index name in the database.

Given a Connection object, a string table_name and string index name, return True if an index of the given name on the given table exists, false otherwise.

The DefaultDialect implements this in terms of the Dialect.has_table() and Dialect.get_indexes() methods, however dialects can implement a more performant version.

New in version 1.4.

method sqlalchemy.engine.Dialect.has_sequence(connection, sequence_name, schema=None, **kw)

Check the existence of a particular sequence in the database.

Given a Connection object and a string sequence_name, return True if the given sequence exists in the database, False otherwise.

method sqlalchemy.engine.Dialect.has_table(connection, table_name, schema=None, **kw)

For internal dialect use, check the existence of a particular table in the database.

Given a Connection object, a string table_name and optional schema name, return True if the given table exists in the database, False otherwise.

This method serves as the underlying implementation of the public facing Inspector.has_table() method, and is also used internally to implement the “checkfirst” behavior for methods like Table.create() and MetaData.create_all().

Note

This method is used internally by SQLAlchemy, and is published so that third-party dialects may provide an implementation. It is not the public API for checking for table presence. Please use the Inspector.has_table() method. Alternatively, for legacy cross-compatibility, the Engine.has_table() method may be used.

method sqlalchemy.engine.Dialect.initialize(connection)

Called during strategized creation of the dialect with a connection.

Allows dialects to configure options based on server version info or other properties.

The connection passed here is a SQLAlchemy Connection object, with full capabilities.

The initialize() method of the base dialect should be called via super().

Note

as of SQLAlchemy 1.4, this method is called before any Dialect.on_connect() hooks are called.

method sqlalchemy.engine.Dialect.is_disconnect(e, connection, cursor)

Return True if the given DB-API error indicates an invalid connection

classmethod sqlalchemy.engine.Dialect.load_provisioning()

set up the provision.py module for this dialect.

For dialects that include a provision.py module that sets up provisioning followers, this method should initiate that process.

A typical implementation would be:

@classmethod
def load_provisioning(cls):
    __import__("mydialect.provision")

The default method assumes a module named provision.py inside the owning package of the current dialect, based on the __module__ attribute:

@classmethod
def load_provisioning(cls):
    package = ".".join(cls.__module__.split(".")[0:-1])
    try:
        __import__(package + ".provision")
    except ImportError:
        pass

New in version 1.3.14.

method sqlalchemy.engine.Dialect.normalize_name(name)

convert the given name to lowercase if it is detected as case insensitive.

This method is only used if the dialect defines requires_name_normalize=True.

method sqlalchemy.engine.Dialect.on_connect()

return a callable which sets up a newly created DBAPI connection.

The callable should accept a single argument “conn” which is the DBAPI connection itself. The inner callable has no return value.

E.g.:

class MyDialect(default.DefaultDialect):
    # ...

    def on_connect(self):
        def do_on_connect(connection):
            connection.execute("SET SPECIAL FLAGS etc")

        return do_on_connect

This is used to set dialect-wide per-connection options such as isolation modes, Unicode modes, etc.

The “do_on_connect” callable is invoked by using the PoolEvents.connect() event hook, then unwrapping the DBAPI connection and passing it into the callable.

Changed in version 1.4: the on_connect hook is no longer called twice for the first connection of a dialect. The on_connect hook is still called before the Dialect.initialize() method however.

Changed in version 1.4.3: the on_connect hook is invoked from a new method on_connect_url that passes the URL that was used to create the connect args. Dialects can implement on_connect_url instead of on_connect if they need the URL object that was used for the connection in order to get additional context.

If None is returned, no event listener is generated.

Returns:

a callable that accepts a single DBAPI connection as an argument, or None.

See also

Dialect.connect() - allows the DBAPI connect() sequence itself to be controlled.

Dialect.on_connect_url() - supersedes Dialect.on_connect() to also receive the URL object in context.

method sqlalchemy.engine.Dialect.on_connect_url(url)

return a callable which sets up a newly created DBAPI connection.

This method is a new hook that supersedes the Dialect.on_connect() method when implemented by a dialect. When not implemented by a dialect, it invokes the Dialect.on_connect() method directly to maintain compatibility with existing dialects. There is no deprecation for Dialect.on_connect() expected.

The callable should accept a single argument “conn” which is the DBAPI connection itself. The inner callable has no return value.

E.g.:

class MyDialect(default.DefaultDialect):
    # ...

    def on_connect_url(self, url):
        def do_on_connect(connection):
            connection.execute("SET SPECIAL FLAGS etc")

        return do_on_connect

This is used to set dialect-wide per-connection options such as isolation modes, Unicode modes, etc.

This method differs from Dialect.on_connect() in that it is passed the URL object that’s relevant to the connect args. Normally the only way to get this is from the Dialect.on_connect() hook is to look on the Engine itself, however this URL object may have been replaced by plugins.

Note

The default implementation of Dialect.on_connect_url() is to invoke the Dialect.on_connect() method. Therefore if a dialect implements this method, the Dialect.on_connect() method will not be called unless the overriding dialect calls it directly from here.

New in version 1.4.3: added Dialect.on_connect_url() which normally calls into Dialect.on_connect().

Parameters:

url – a URL object representing the URL that was passed to the Dialect.create_connect_args() method.

Returns:

a callable that accepts a single DBAPI connection as an argument, or None.

See also

Dialect.on_connect()

method sqlalchemy.engine.Dialect.reset_isolation_level(dbapi_conn)

Given a DBAPI connection, revert its isolation to the default.

Note that this is a dialect-level method which is used as part of the implementation of the Connection and Engine isolation level facilities; these APIs should be preferred for most typical use cases.

See also

Connection.get_isolation_level() - view current level

Connection.default_isolation_level - view default level

Connection.execution_options.isolation_level - set per Connection isolation level

create_engine.isolation_level - set per Engine isolation level

method sqlalchemy.engine.Dialect.set_isolation_level(dbapi_conn, level)

Given a DBAPI connection, set its isolation level.

Note that this is a dialect-level method which is used as part of the implementation of the Connection and Engine isolation level facilities; these APIs should be preferred for most typical use cases.

See also

Connection.get_isolation_level() - view current level

Connection.default_isolation_level - view default level

Connection.execution_options.isolation_level - set per Connection isolation level

create_engine.isolation_level - set per Engine isolation level

attribute sqlalchemy.engine.Dialect.supports_statement_cache = True

indicates if this dialect supports caching.

All dialects that are compatible with statement caching should set this flag to True directly on each dialect class and subclass that supports it. SQLAlchemy tests that this flag is locally present on each dialect subclass before it will use statement caching. This is to provide safety for legacy or new dialects that are not yet fully tested to be compliant with SQL statement caching.

New in version 1.4.5.

See also

Caching for Third Party Dialects

classmethod sqlalchemy.engine.Dialect.type_descriptor(typeobj)

Transform a generic type to a dialect-specific type.

Dialect classes will usually use the adapt_type() function in the types module to accomplish this.

The returned result is cached per dialect class so can contain no dialect-instance state.

class sqlalchemy.engine.default.DefaultExecutionContext

Members

create_cursor(), current_parameters, get_current_parameters(), get_lastrowid(), get_out_parameter_values(), get_result_processor(), handle_dbapi_exception(), lastrow_has_defaults(), post_exec(), pre_exec(), should_autocommit_text()

Class signature

class sqlalchemy.engine.default.DefaultExecutionContext (sqlalchemy.engine.interfaces.ExecutionContext)

method sqlalchemy.engine.default.DefaultExecutionContext.create_cursor()

Return a new cursor generated from this ExecutionContext’s connection.

Some dialects may wish to change the behavior of connection.cursor(), such as postgresql which may return a PG “server side” cursor.

attribute sqlalchemy.engine.default.DefaultExecutionContext.current_parameters = None

A dictionary of parameters applied to the current row.

This attribute is only available in the context of a user-defined default generation function, e.g. as described at Context-Sensitive Default Functions. It consists of a dictionary which includes entries for each column/value pair that is to be part of the INSERT or UPDATE statement. The keys of the dictionary will be the key value of each Column, which is usually synonymous with the name.

Note that the DefaultExecutionContext.current_parameters attribute does not accommodate for the “multi-values” feature of the Insert.values() method. The DefaultExecutionContext.get_current_parameters() method should be preferred.

See also

DefaultExecutionContext.get_current_parameters()

Context-Sensitive Default Functions

method sqlalchemy.engine.default.DefaultExecutionContext.get_current_parameters(isolate_multiinsert_groups=True)

Return a dictionary of parameters applied to the current row.

This method can only be used in the context of a user-defined default generation function, e.g. as described at Context-Sensitive Default Functions. When invoked, a dictionary is returned which includes entries for each column/value pair that is part of the INSERT or UPDATE statement. The keys of the dictionary will be the key value of each Column, which is usually synonymous with the name.

Parameters:

isolate_multiinsert_groups=True – indicates that multi-valued INSERT constructs created using Insert.values() should be handled by returning only the subset of parameters that are local to the current column default invocation. When False, the raw parameters of the statement are returned including the naming convention used in the case of multi-valued INSERT.

New in version 1.2: added DefaultExecutionContext.get_current_parameters() which provides more functionality over the existing DefaultExecutionContext.current_parameters attribute.

See also

DefaultExecutionContext.current_parameters

Context-Sensitive Default Functions

method sqlalchemy.engine.default.DefaultExecutionContext.get_lastrowid()

return self.cursor.lastrowid, or equivalent, after an INSERT.

This may involve calling special cursor functions, issuing a new SELECT on the cursor (or a new one), or returning a stored value that was calculated within post_exec().

This function will only be called for dialects which support “implicit” primary key generation, keep preexecute_autoincrement_sequences set to False, and when no explicit id value was bound to the statement.

The function is called once for an INSERT statement that would need to return the last inserted primary key for those dialects that make use of the lastrowid concept. In these cases, it is called directly after ExecutionContext.post_exec().

method sqlalchemy.engine.default.DefaultExecutionContext.get_out_parameter_values(names)

Return a sequence of OUT parameter values from a cursor.

For dialects that support OUT parameters, this method will be called when there is a SQLCompiler object which has the SQLCompiler.has_out_parameters flag set. This flag in turn will be set to True if the statement itself has BindParameter objects that have the .isoutparam flag set which are consumed by the SQLCompiler.visit_bindparam() method. If the dialect compiler produces BindParameter objects with .isoutparam set which are not handled by SQLCompiler.visit_bindparam(), it should set this flag explicitly.

The list of names that were rendered for each bound parameter is passed to the method. The method should then return a sequence of values corresponding to the list of parameter objects. Unlike in previous SQLAlchemy versions, the values can be the raw values from the DBAPI; the execution context will apply the appropriate type handler based on what’s present in self.compiled.binds and update the values. The processed dictionary will then be made available via the .out_parameters collection on the result object. Note that SQLAlchemy 1.4 has multiple kinds of result object as part of the 2.0 transition.

New in version 1.4: - added ExecutionContext.get_out_parameter_values(), which is invoked automatically by the DefaultExecutionContext when there are BindParameter objects with the .isoutparam flag set. This replaces the practice of setting out parameters within the now-removed get_result_proxy() method.

method sqlalchemy.engine.default.DefaultExecutionContext.get_result_processor(type_, colname, coltype)

Return a ‘result processor’ for a given type as present in cursor.description.

This has a default implementation that dialects can override for context-sensitive result type handling.

method sqlalchemy.engine.default.DefaultExecutionContext.handle_dbapi_exception(e)

Receive a DBAPI exception which occurred upon execute, result fetch, etc.

method sqlalchemy.engine.default.DefaultExecutionContext.lastrow_has_defaults()

Return True if the last INSERT or UPDATE row contained inlined or database-side defaults.

method sqlalchemy.engine.default.DefaultExecutionContext.post_exec()

Called after the execution of a compiled statement.

If a compiled statement was passed to this ExecutionContext, the last_insert_ids, last_inserted_params, etc. datamembers should be available after this method completes.

method sqlalchemy.engine.default.DefaultExecutionContext.pre_exec()

Called before an execution of a compiled statement.

If a compiled statement was passed to this ExecutionContext, the statement and parameters datamembers must be initialized after this statement is complete.

method sqlalchemy.engine.default.DefaultExecutionContext.should_autocommit_text(statement)

Parse the given textual statement and return True if it refers to a “committable” statement

class sqlalchemy.engine.ExecutionContext

A messenger object for a Dialect that corresponds to a single execution.

ExecutionContext should have these data members:

Members

create_cursor(), get_out_parameter_values(), get_rowcount(), handle_dbapi_exception(), lastrow_has_defaults(), post_exec(), pre_exec(), should_autocommit_text()

connection

Connection object which can be freely used by default value generators to execute SQL. This Connection should reference the same underlying connection/transactional resources of root_connection.

root_connection

Connection object which is the source of this ExecutionContext. This Connection may have close_with_result=True set, in which case it can only be used once.

dialect

dialect which created this ExecutionContext.

cursor

DB-API cursor procured from the connection,

compiled

if passed to constructor, sqlalchemy.engine.base.Compiled object being executed,

statement

string version of the statement to be executed. Is either passed to the constructor, or must be created from the sql.Compiled object by the time pre_exec() has completed.

parameters

bind parameters passed to the execute() method. For compiled statements, this is a dictionary or list of dictionaries. For textual statements, it should be in a format suitable for the dialect’s paramstyle (i.e. dict or list of dicts for non positional, list or list of lists/tuples for positional).

isinsert

True if the statement is an INSERT.

isupdate

True if the statement is an UPDATE.

should_autocommit

True if the statement is a “committable” statement.

prefetch_cols

a list of Column objects for which a client-side default was fired off. Applies to inserts and updates.

postfetch_cols

a list of Column objects for which a server-side default or inline SQL expression value was fired off. Applies to inserts and updates.

method sqlalchemy.engine.ExecutionContext.create_cursor()

Return a new cursor generated from this ExecutionContext’s connection.

Some dialects may wish to change the behavior of connection.cursor(), such as postgresql which may return a PG “server side” cursor.

method sqlalchemy.engine.ExecutionContext.get_out_parameter_values(out_param_names)

Return a sequence of OUT parameter values from a cursor.

For dialects that support OUT parameters, this method will be called when there is a SQLCompiler object which has the SQLCompiler.has_out_parameters flag set. This flag in turn will be set to True if the statement itself has BindParameter objects that have the .isoutparam flag set which are consumed by the SQLCompiler.visit_bindparam() method. If the dialect compiler produces BindParameter objects with .isoutparam set which are not handled by SQLCompiler.visit_bindparam(), it should set this flag explicitly.

The list of names that were rendered for each bound parameter is passed to the method. The method should then return a sequence of values corresponding to the list of parameter objects. Unlike in previous SQLAlchemy versions, the values can be the raw values from the DBAPI; the execution context will apply the appropriate type handler based on what’s present in self.compiled.binds and update the values. The processed dictionary will then be made available via the .out_parameters collection on the result object. Note that SQLAlchemy 1.4 has multiple kinds of result object as part of the 2.0 transition.

New in version 1.4: - added ExecutionContext.get_out_parameter_values(), which is invoked automatically by the DefaultExecutionContext when there are BindParameter objects with the .isoutparam flag set. This replaces the practice of setting out parameters within the now-removed get_result_proxy() method.

method sqlalchemy.engine.ExecutionContext.get_rowcount()

Return the DBAPI cursor.rowcount value, or in some cases an interpreted value.

See CursorResult.rowcount for details on this.

method sqlalchemy.engine.ExecutionContext.handle_dbapi_exception(e)

Receive a DBAPI exception which occurred upon execute, result fetch, etc.

method sqlalchemy.engine.ExecutionContext.lastrow_has_defaults()

Return True if the last INSERT or UPDATE row contained inlined or database-side defaults.

method sqlalchemy.engine.ExecutionContext.post_exec()

Called after the execution of a compiled statement.

If a compiled statement was passed to this ExecutionContext, the last_insert_ids, last_inserted_params, etc. datamembers should be available after this method completes.

method sqlalchemy.engine.ExecutionContext.pre_exec()

Called before an execution of a compiled statement.

If a compiled statement was passed to this ExecutionContext, the statement and parameters datamembers must be initialized after this statement is complete.

method sqlalchemy.engine.ExecutionContext.should_autocommit_text(statement)

Parse the given textual statement and return True if it refers to a “committable” statement

class sqlalchemy.sql.compiler.GenericTypeCompiler(dialect)

Class signature

class sqlalchemy.sql.compiler.GenericTypeCompiler (sqlalchemy.sql.compiler.TypeCompiler)

class sqlalchemy.log.Identified
class sqlalchemy.sql.compiler.IdentifierPreparer(dialect, initial_quote='"', final_quote=None, escape_quote='"', quote_case_sensitive_collations=True, omit_schema=False)

Members

__init__(), format_column(), format_label_name(), format_schema(), format_table(), format_table_seq(), quote(), quote_identifier(), quote_schema(), schema_for_object, unformat_identifiers(), validate_sql_phrase()

Handle quoting and case-folding of identifiers based on options.

method sqlalchemy.sql.compiler.IdentifierPreparer.__init__(dialect, initial_quote='"', final_quote=None, escape_quote='"', quote_case_sensitive_collations=True, omit_schema=False)

Construct a new IdentifierPreparer object.

initial_quote

Character that begins a delimited identifier.

final_quote

Character that ends a delimited identifier. Defaults to initial_quote.

omit_schema

Prevent prepending schema name. Useful for databases that do not support schemae.

method sqlalchemy.sql.compiler.IdentifierPreparer.format_column(column, use_table=False, name=None, table_name=None, use_schema=False, anon_map=None)

Prepare a quoted column name.

method sqlalchemy.sql.compiler.IdentifierPreparer.format_label_name(name, anon_map=None)

Prepare a quoted column name.

method sqlalchemy.sql.compiler.IdentifierPreparer.format_schema(name)

Prepare a quoted schema name.

method sqlalchemy.sql.compiler.IdentifierPreparer.format_table(table, use_schema=True, name=None)

Prepare a quoted table and schema name.

method sqlalchemy.sql.compiler.IdentifierPreparer.format_table_seq(table, use_schema=True)

Format table name and schema as a tuple.

method sqlalchemy.sql.compiler.IdentifierPreparer.quote(ident, force=None)

Conditionally quote an identifier.

The identifier is quoted if it is a reserved word, contains quote-necessary characters, or is an instance of quoted_name which includes quote set to True.

Subclasses can override this to provide database-dependent quoting behavior for identifier names.

Parameters:
method sqlalchemy.sql.compiler.IdentifierPreparer.quote_identifier(value)

Quote an identifier.

Subclasses should override this to provide database-dependent quoting behavior.

method sqlalchemy.sql.compiler.IdentifierPreparer.quote_schema(schema, force=None)

Conditionally quote a schema name.

The name is quoted if it is a reserved word, contains quote-necessary characters, or is an instance of quoted_name which includes quote set to True.

Subclasses can override this to provide database-dependent quoting behavior for schema names.

Parameters:
attribute sqlalchemy.sql.compiler.IdentifierPreparer.schema_for_object = operator.attrgetter('schema')

Return the .schema attribute for an object.

For the default IdentifierPreparer, the schema for an object is always the value of the “.schema” attribute. if the preparer is replaced with one that has a non-empty schema_translate_map, the value of the “.schema” attribute is rendered a symbol that will be converted to a real schema name from the mapping post-compile.

method sqlalchemy.sql.compiler.IdentifierPreparer.unformat_identifiers(identifiers)

Unpack ‘schema.table.column’-like strings into components.

method sqlalchemy.sql.compiler.IdentifierPreparer.validate_sql_phrase(element, reg)

keyword sequence filter.

a filter for elements that are intended to represent keyword sequences, such as “INITIALLY”, “INITIALLY DEFERRED”, etc. no special characters should be present.

New in version 1.3.

class sqlalchemy.sql.compiler.SQLCompiler(dialect, statement, cache_key=None, column_keys=None, for_executemany=False, linting=symbol('NO_LINTING'), **kwargs)

Default implementation of Compiled.

Compiles ClauseElement objects into SQL strings.

Members

__init__(), ansi_bind_rules, construct_params(), current_executable, default_from(), delete_extra_from_clause(), escaped_bind_names, get_select_precolumns(), group_by_clause(), has_out_parameters, insert_single_values_expr, isdelete, literal_execute_params, order_by_clause(), params, positiontup, post_compile_params, postfetch_lastrowid, render_literal_value(), render_table_with_column_in_update_from, returning, returning_precedes_values, sql_compiler, translate_select_structure, update_from_clause(), update_limit_clause(), update_tables_clause()

Class signature

class sqlalchemy.sql.compiler.SQLCompiler (sqlalchemy.sql.compiler.Compiled)

method sqlalchemy.sql.compiler.SQLCompiler.__init__(dialect, statement, cache_key=None, column_keys=None, for_executemany=False, linting=symbol('NO_LINTING'), **kwargs)

Construct a new SQLCompiler object.

Parameters:

  • dialect – Dialect to be used

  • statement – ClauseElement to be compiled

  • column_keys – a list of column names to be compiled into an INSERT or UPDATE statement.

  • for_executemany – whether INSERT / UPDATE statements should expect that they are to be invoked in an “executemany” style, which may impact how the statement will be expected to return the values of defaults and autoincrement / sequences and similar. Depending on the backend and driver in use, support for retrieving these values may be disabled which means SQL expressions may be rendered inline, RETURNING may not be rendered, etc.

  • kwargs – additional keyword arguments to be consumed by the superclass.

attribute sqlalchemy.sql.compiler.SQLCompiler.ansi_bind_rules = False

SQL 92 doesn’t allow bind parameters to be used in the columns clause of a SELECT, nor does it allow ambiguous expressions like “? = ?”. A compiler subclass can set this flag to False if the target driver/DB enforces this

method sqlalchemy.sql.compiler.SQLCompiler.construct_params(params=None, _group_number=None, _check=True, extracted_parameters=None, escape_names=True)

return a dictionary of bind parameter keys and values

attribute sqlalchemy.sql.compiler.SQLCompiler.current_executable

Return the current ‘executable’ that is being compiled.

This is currently the Select, Insert, Update, Delete, CompoundSelect object that is being compiled. Specifically it’s assigned to the self.stack list of elements.

When a statement like the above is being compiled, it normally is also assigned to the .statement attribute of the Compiler object. However, all SQL constructs are ultimately nestable, and this attribute should never be consulted by a visit_ method, as it is not guaranteed to be assigned nor guaranteed to correspond to the current statement being compiled.

New in version 1.3.21: For compatibility with previous versions, use the following recipe:

statement = getattr(self, "current_executable", False)
if statement is False:
    statement = self.stack[-1]["selectable"]

For versions 1.4 and above, ensure only .current_executable is used; the format of “self.stack” may change.

method sqlalchemy.sql.compiler.SQLCompiler.default_from()

Called when a SELECT statement has no froms, and no FROM clause is to be appended.

Gives Oracle a chance to tack on a FROM DUAL to the string output.

method sqlalchemy.sql.compiler.SQLCompiler.delete_extra_from_clause(update_stmt, from_table, extra_froms, from_hints, **kw)

Provide a hook to override the generation of an DELETE..FROM clause.

This can be used to implement DELETE..USING for example.

MySQL and MSSQL override this.

attribute sqlalchemy.sql.compiler.SQLCompiler.escaped_bind_names = {}

Late escaping of bound parameter names that has to be converted to the original name when looking in the parameter dictionary.

method sqlalchemy.sql.compiler.SQLCompiler.get_select_precolumns(select, **kw)

Called when building a SELECT statement, position is just before column list.

method sqlalchemy.sql.compiler.SQLCompiler.group_by_clause(select, **kw)

allow dialects to customize how GROUP BY is rendered.

attribute sqlalchemy.sql.compiler.SQLCompiler.has_out_parameters = False

if True, there are bindparam() objects that have the isoutparam flag set.

attribute sqlalchemy.sql.compiler.SQLCompiler.insert_single_values_expr = None

When an INSERT is compiled with a single set of parameters inside a VALUES expression, the string is assigned here, where it can be used for insert batching schemes to rewrite the VALUES expression.

New in version 1.3.8.

attribute sqlalchemy.sql.compiler.SQLCompiler.isdelete = False

class-level defaults which can be set at the instance level to define if this Compiled instance represents INSERT/UPDATE/DELETE

attribute sqlalchemy.sql.compiler.SQLCompiler.literal_execute_params = frozenset({})

bindparameter objects that are rendered as literal values at statement execution time.

method sqlalchemy.sql.compiler.SQLCompiler.order_by_clause(select, **kw)

allow dialects to customize how ORDER BY is rendered.

attribute sqlalchemy.sql.compiler.SQLCompiler.params

Return the bind param dictionary embedded into this compiled object, for those values that are present.

See also

How do I render SQL expressions as strings, possibly with bound parameters inlined? - includes a usage example for debugging use cases.

attribute sqlalchemy.sql.compiler.SQLCompiler.positiontup = None

for a compiled construct that uses a positional paramstyle, will be a sequence of strings, indicating the names of bound parameters in order.

This is used in order to render bound parameters in their correct order, and is combined with the Compiled.params dictionary to render parameters.

See also

How do I render SQL expressions as strings, possibly with bound parameters inlined? - includes a usage example for debugging use cases.

attribute sqlalchemy.sql.compiler.SQLCompiler.post_compile_params = frozenset({})

bindparameter objects that are rendered as bound parameter placeholders at statement execution time.

attribute sqlalchemy.sql.compiler.SQLCompiler.postfetch_lastrowid = False

if True, and this in insert, use cursor.lastrowid to populate result.inserted_primary_key.

method sqlalchemy.sql.compiler.SQLCompiler.render_literal_value(value, type_)

Render the value of a bind parameter as a quoted literal.

This is used for statement sections that do not accept bind parameters on the target driver/database.

This should be implemented by subclasses using the quoting services of the DBAPI.

attribute sqlalchemy.sql.compiler.SQLCompiler.render_table_with_column_in_update_from = False

set to True classwide to indicate the SET clause in a multi-table UPDATE statement should qualify columns with the table name (i.e. MySQL only)

attribute sqlalchemy.sql.compiler.SQLCompiler.returning = None

holds the “returning” collection of columns if the statement is CRUD and defines returning columns either implicitly or explicitly

attribute sqlalchemy.sql.compiler.SQLCompiler.returning_precedes_values = False

set to True classwide to generate RETURNING clauses before the VALUES or WHERE clause (i.e. MSSQL)

attribute sqlalchemy.sql.compiler.SQLCompiler.sql_compiler
attribute sqlalchemy.sql.compiler.SQLCompiler.translate_select_structure = None

if not None, should be a callable which accepts (select_stmt, **kw) and returns a select object. this is used for structural changes mostly to accommodate for LIMIT/OFFSET schemes

method sqlalchemy.sql.compiler.SQLCompiler.update_from_clause(update_stmt, from_table, extra_froms, from_hints, **kw)

Provide a hook to override the generation of an UPDATE..FROM clause.

MySQL and MSSQL override this.

method sqlalchemy.sql.compiler.SQLCompiler.update_limit_clause(update_stmt)

Provide a hook for MySQL to add LIMIT to the UPDATE

method sqlalchemy.sql.compiler.SQLCompiler.update_tables_clause(update_stmt, from_table, extra_froms, **kw)

Provide a hook to override the initial table clause in an UPDATE statement.

MySQL overrides this.

class sqlalchemy.sql.compiler.StrSQLCompiler(dialect, statement, cache_key=None, column_keys=None, for_executemany=False, linting=symbol('NO_LINTING'), **kwargs)

A SQLCompiler subclass which allows a small selection of non-standard SQL features to render into a string value.

The StrSQLCompiler is invoked whenever a Core expression element is directly stringified without calling upon the ClauseElement.compile() method. It can render a limited set of non-standard SQL constructs to assist in basic stringification, however for more substantial custom or dialect-specific SQL constructs, it will be necessary to make use of ClauseElement.compile() directly.

See also

How do I render SQL expressions as strings, possibly with bound parameters inlined?

Members

delete_extra_from_clause(), update_from_clause()

Class signature

class sqlalchemy.sql.compiler.StrSQLCompiler (sqlalchemy.sql.compiler.SQLCompiler)

method sqlalchemy.sql.compiler.StrSQLCompiler.delete_extra_from_clause(update_stmt, from_table, extra_froms, from_hints, **kw)

Provide a hook to override the generation of an DELETE..FROM clause.

This can be used to implement DELETE..USING for example.

MySQL and MSSQL override this.

method sqlalchemy.sql.compiler.StrSQLCompiler.update_from_clause(update_stmt, from_table, extra_froms, from_hints, **kw)

Provide a hook to override the generation of an UPDATE..FROM clause.

MySQL and MSSQL override this.

class sqlalchemy.engine.AdaptedConnection

Interface of an adapted connection object to support the DBAPI protocol.

Used by asyncio dialects to provide a sync-style pep-249 facade on top of the asyncio connection/cursor API provided by the driver.

Members

driver_connection, run_async()

New in version 1.4.24.

attribute sqlalchemy.engine.AdaptedConnection.driver_connection

The connection object as returned by the driver after a connect.

method sqlalchemy.engine.AdaptedConnection.run_async(fn)

Run the awaitable returned by the given function, which is passed the raw asyncio driver connection.

This is used to invoke awaitable-only methods on the driver connection within the context of a “synchronous” method, like a connection pool event handler.

E.g.:

engine = create_async_engine(...)

@event.listens_for(engine.sync_engine, "connect")
def register_custom_types(dbapi_connection, ...):
    dbapi_connection.run_async(
        lambda connection: connection.set_type_codec(
            'MyCustomType', encoder, decoder, ...
        )
    )

New in version 1.4.30.

See also

Using awaitable-only driver methods in connection pool and other events